Current automotive systems manage the charging of a vehicle battery by regulating the power generation of the alternator. In these systems, the voltage output of the alternator is regulated to, first, provide the necessary electrical power for the vehicle and passenger needs and, second, provide charge to the vehicle's battery. Typically, the alternator regulation scheme operates on the simple principle that an increase in a generated voltage of the alternator will charge the battery if it is at a lower voltage level. This principle is the basis for all prior art charging schemes.
It is well known in the prior art that a reduction in the power generated by the alternator increases fuel efficiency. Furthermore, continuous overcharging of a battery leads to a decrease in battery life and has other undesirable effects. In order to increase fuel efficiency and reduce overcharging in order to increase battery life, vehicles are operated so as to avoid the charging of a fully charged battery by the alternator. This is accomplished by controlling the voltage generated by the alternator, which reduces the current sent to the battery. There are, however, a number of disadvantages to this voltage-control based system. First, under most normal conditions, the electrical draw of the loads of a vehicle take precedence over the charging of the battery. Some of the loads of the vehicle (e.g., fuel pump, heated seats) may require a higher voltage under certain operating conditions and, thus, a fully-charged battery would still be subjected to an increased voltage under these conditions. Thus, a fully-charged battery would still be receiving a current from the alternator under these conditions. Second, even in cases where the vehicle loads do not require an increased voltage level, a non-zero current is still delivered to a fully-charged battery under voltage control.
There exists a need for an improved alternator control method that reduces or eliminates the delivery of unnecessary and potentially harmful current to a vehicle's fully-charged battery.